Antireflective (AR) coatings are known in the art. For example, AR coatings in the visible range are widely used on glass in electronics, lighting, appliances, architectural, and display applications. There are various techniques for reducing the reflection of visible light moving from air onto and through a glass surface. One technique is to apply a thin layer of material onto the surface of a glass substrate, interposing the thin layer between the glass substrate and the air. Optimally, the index of refraction of the thin layer is equal to the square root of the product of the index of refraction of visible light through air and the index of refraction of visible light through the glass substrate. Achieving this optimal index of refraction is difficult however.
Further, in many of these applications, tempered or heat-strengthened glass may be required. Tempering or heat strengthening of the glass is sometimes done prior to the deposition of the AR coating to avoid unwanted changes in the optical, mechanical, or aesthetic quality of the coating as a consequence of exposing the coating to the high temperatures required for tempering and other forms of heat treatment. However, this “temper then coat” method may be undesirable in certain circumstances.
Further, a coat then temper technique may create additional problems. When glass is coated and then tempered, the result of the tempering process may produce undesirable optical flaws in the overall glass product. For example, the color shift, or ΔE, in the tempered, coated glass product may render the glass unusable. Further, techniques that maintain the optical characteristics of a substrate with an AR between pre and post tempering are desirable (e.g., one AR coating may be applied in more than one situation).
Thus, it will be appreciated that there exists a need in the art for improved antireflective (AR) coatings (e.g., temperable AR coatings) for coated articles such as windows and the like.
In certain example embodiments, there is provided a coated article comprising an antireflective coating supported by a major surface of a substrate, the substrate being heat treated together with the antireflective coating, wherein the antireflective coating comprises, in order moving away from the substrate: a medium index layer comprising silicon oxynitride and having a index of refraction of from about 1.65 to 2.0 at 380 nm, 550 nm, and 780 nm wavelengths, a high index layer having an index of refraction of at least about 2.0 at 380 nm, 550 nm, and 780 nm wavelengths, and a low index layer having an index of refraction of from about 1.4 to 1.6 at 380 nm, 550 nm, and 780 nm wavelengths, wherein the medium index layer has compressive residual stress after heat treatment.
In certain example embodiments, there is provided a heat treatable coated article, the coated article comprising: an antireflective coating supported by a major surface of a substrate, wherein the antireflective coating comprises, in order moving away from the substrate: a medium index layer comprising silicon oxynitride and having a index of refraction of from about 1.65 to 2.0 at 380 nm, 550 nm, and 780 nm wavelengths, a high index layer having an index of refraction higher than that of the medium index layer at 380 nm, 550 nm, and 780 nm wavelengths, and a low index layer having an index of refraction lower than that of the medium index layer at 380 nm, 550 nm, and 780 nm wavelengths, wherein the medium index layer and the low index layer have compressive residual stress after any heat treatment, the high index layer has tensile residual stress after any heat treatment, and the antireflective coating has a net compressive residual stress.
In certain example embodiments, there is provided a heat treatable coated article, the coated article comprising an antireflective coating supported by a major surface of a substrate, wherein the antireflective coating comprises, in order moving away from the substrate: a medium index silicon-inclusive layer having a index of refraction of 1.8 or less 550 nm and 780 nm wavelengths and 2.0 or less at 380 nm, a high index layer having an index of refraction higher than that of the medium index layer at 380 nm, 550 nm, and 780 nm wavelengths, wherein the high index layer has a thickness no greater than about 20 nm, and a low index layer having an index of refraction lower than that of the medium index layer at 380 nm, 550 nm, and 780 nm wavelengths, wherein the medium index layer and the low index layer have compressive residual stress, the high index layer has tensile residual stress, and the antireflective coating has a net compressive residual stress.
In certain example embodiments, there is provided a method of making a coated article with a three-layered antireflection coating, the method comprising: disposing a medium index layer, directly or indirectly, on a glass substrate; disposing a high index layer over and contacting the medium index layer; disposing a low index layer over and contacting the high index layer; and heat-treating the glass substrate with the antireflective coating thereon, and wherein the coated article has a net compressive residual stress.
In certain example embodiments, a method of making a coated article is provided. A glass substrate is provided. A silicon-inclusive medium index layer is disposed, directly or indirectly, on a first major surface of the substrate. A high index layer is disposed over and contacting the medium index layer, the high index layer having a thickness of at least 85 nm. A low index layer is disposed over and contacting the high index layer. The substrate is heat treated with the medium, high, and low index layers disposed thereon. The coated article has a ΔE* value of less than 3 between as deposited and heat treated states.
In certain example embodiments, a method of making a coated article is provided. A glass substrate is provided. A silicon-inclusive medium index layer is disposed, directly or indirectly, on a first major surface of the substrate. A high index layer is disposed over and contacting the medium index layer, the high index layer having a thickness of at least 85 nm. A low index layer is disposed over and contacting the high index layer. The coated article is heat treatable so as to have a ΔE* value of less than 3.
In certain example embodiments, a coated article comprising an antireflective coating supported by a first major surface of a substrate is provided. The antireflective coating comprises, in order moving away from the substrate: a silicon-inclusive medium index layer disposed, directly or indirectly, on the first major surface of the substrate; a high index layer disposed over and contacting the medium index layer, the high index layer having a thickness of at least 85 nm; and a low index layer disposed over and contacting the high index layer. The coated article is heat treatable so as to have a ΔE* value of less than 3.
According to certain example embodiments, A second major surface of the substrate may support a second antireflective coating that comprises, in order moving away from the substrate: a second silicon-inclusive medium index layer, directly or indirectly, on the second major surface of the substrate; a second high index layer over and contacting the second medium index layer, the high index layer having a thickness of at least 85 nm; and a second low index layer over and contacting the second high index layer. All said layers may be disposed on the substrate prior to any heat treating. In such example embodiments, the ΔE* value may be less than 2 and sometimes less than or equal to about 1.5.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.